A vertical metal oxide semiconductor (MOS) transistor with a trench gate in trenches has the gate dielectric layer and gate extending down the trenches past the body, abutting a vertical drift region under the body. The trenches have to be deeper than desired to support a desired operating voltage, because the gate dielectric layer cannot support a high electric field in the drift region. Increasing the thickness of the gate dielectric layer undesirably increases the resistance of the channel region in the on state.